STM32 dual regular simultaneous mode with DMA

I have a STM32F303K8T6 uC and would like to read ADC1 and ADC2 with DMA, triggered by TIM2 at the same time instance. The triggering by TIM2 works fine, but then only ADC1 is read out and not ADC2. Any suggestions what I need to change? Also when I set the adc_array to uint32_t, the upper and the lower bits are still only from ADC1.